We have been building a local-first browser app (PWA) for personal finance, based on double-entry accounting. https://finbodhi.com/

It's not always offline. We do use online services like firebase for auth and subscription, and some service to fetch commodity prices etc, but rest of the data is stored in browser storage (sqlite) and backed to local disk and dropbox. We also syncs data across devices, always encrypting data in transit. We use Evolu for sync.

For most personal applications, this model seems to fit. If you figure out sync, the development model is actually nicer than web apps. There is no need for dealing with calls over network for each action. It does make some things more difficult. Debugging, migrations etc.